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    <title>Document</title>
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        div {
            width: 200px;
            height: 200px;
            background-color: aqua;
        }
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<body>
    <div>

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    <script>
        // 调整窗口大小resize
        div = document.querySelector('div');
        window.addEventListener('resize', function(){
            console.log('窗口变了！');
            // window.innerWidth 窗口宽度
            if(window.innerWidth < 500) {
                div.style.display = 'none';
            }
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</body>
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